Telephone instrument



Ju-ne 10, 1941. A TURNBULL, JR, ErAL 2,245,511

TELEPHONE .INSTRUMENT v Filed Dec. 4; 1937V y 2 Sheets-Sheet 1 June 10,1941- A. 'ruRNBuLL JR., ErAL 2,245,511 Y TELEPHONE INSTRUMENT Filed D466. 4, 1937 '2 sneetsjsheet 2 ,755151 ,l lill;

`PatentedJune l0, 1941 v UNITED STAT 13s PATENT -o'FFics TELEPHONE msTnUMENT Arthur Turnbull, Jr., Far Hills, and Herbert B.

Warnke, East Orange, N. J., assignors to United States Instrument Corporation, vEast Orange, N. J., a corporation of New Jersey -.lipnlicatimi December.' 4, 1937, semina. 178,150 a 9 claims. (ci. 179-119) l This invention relates to telephone instruments and more particularly to instruments of the electro-magnetic type which are adapted to be' used.

either as transmitters or receivers. Instruments of this type are adapted to be used in circuits which do`not or need..not include a source of electric energy other-than the instrument which,`

at any given moment, is serving as the transmitter, and such instruments are therefore v known as sound-powered telephone instru-a A second object is the provision of s uch an inture is supported at a point between its ends, so that both ends of the armature may vibrate in response to movements of the diaphragm.

Another object isthe provision of an instrument in which the usual coil is replaced by a relatively few-turns of insulated wire wound directly upon the armature itself, and adapted to vibrate therewith, without substantially reducing the responsiveness of the armature.

lAnother object is the provisionl of a instrument of the class described, mounted upon a backing plate in -such a manner that the'instrument which shall be unusually compact; with` the attendant advantages of such aiconstruction..

Another object is the provision of an instrument of the'class described which shall beextremely eiiicient, the energy losses in the instrument being reduced by reason of the manner in which the.instrument is constructed and as-A- sembled. a

A further object the provision of an instrument of the class described in which the permanent magnets are arranged in such manner as to permit of conveniently magnetizing them in piace, thus promoting ease'of assembly and permitting'the use f sub- :1oA of the present invention is strument may be supported within a casing, by

clamping the casing members against a peripher` al flange on thevbacking plate, no pressure being applied to the periphery' of the diaphragm, as is the usual case.

Other and further objects, features and advan- .tages will be apparent upon a consideration of the following specification taken in connection with the accompanying drawings, in which Figure 1 is a rear elevation, partly in section,

of one form of telephone instrument constructed in accordance withthe present invention;

Figure 2 is a transverse. vertical section on line 2-2 of Figure 1;

Flgure 3 1s a bottom View of the instrument of Figure 1;

- Figure 4 is a top view of the instrument of Figures 1, 2 and 3, partly in section online 4 4 of I Figure 2;

Figure 5 is a fragmentary transverse section illustrating av modified form of armature mountstantially smaller magnets, as will be hereinafter explained.

A further object is the provision of an instrument' comprising permanent magnets, opposed pole-pieces, and an armature extending between Y the pole-pieces and being permanently adjusted in proper spaced relationship thereto.v

A further object is the provision of a modified form in which the armature is mounted in such a manner as to'promote ease and accuracy of 'adjustment when such adjustment becomes desirable.

Another object is the provision of an instrument of the ciass described in' which the vibratory armature is adjustably secured atits respectivel ends, and is coupled to the diaphragm at its midpoint.

A further object is the ment of the class described, in which the armain V;

igure 6 is a fragmentary section on line 6 6 of Figure 5;

Figure 7 isa bottom view of the device of Figures 5and 6; 1 1

Figure 8 is a-rear elevation of a modied form ofinstrument employing an armature supported at a point intermediate its ends;

Figure 9 is a central transverse vertical. sec--` tional view of the instrument of Figure 8;

provision oi' an instiul iied form of instrument in which the armature is adjustably mounted at its respective ends and 1s coupled to the 'diaphragm at its midpoint;

Figure 12 is a central transverse vertical section of the instrument of Figure l1; and

Figure 13 is a horizontal section on line a-a of lFigure l1.

f In order to facilitate an understanding of the telephone invention, reference is made .to the embodiment thereof shown in the accompanying drawings and detailed descriptive language is employed. It will nevertheless be understood that no limitation ofthe invention is thereby intended and that various changes and alterations are contemplated such as would ordinarily occur to one skilled in the art to which .the invention relates. Referring rst to the device of Figures v1 to 4, inclusive,` it will be seen that the usual diaphragm I5 is secured to the forward face of a backing plate t6 by means of a clamping ring I1 secured by screws, annular cushioning gaskets I8 and I9 being preferably interposed between the diaphragm and the backing plate and clamping ring, respectively. The backing plate is provided with a peripheral ange '20 which projects radially beyond the periphery of the diaphragm l5, to provide for clamping 'the instrument in a casing. The l-atter comprises a cupA member 2| and a cover member 22, having threaded engagement with eachother, and being provided with opposed shoulders for gripping the peripherl flange 20 ofthe backing plate therebetween. The

backing plate I6 is cut away as at 23 in order to lighten the instrument as well as to provide clearance for the coupling means extending between the diaphragm and armature.

In .the instrument of the present invention the usual semi-circular or horse-shoe shaped magnets are replaced by straight bar magnets, preferably substantially rectangular in cross section, and v which are preferably formed of. magnetic material of very high coercive force, the preferred material being an alloy of aluminum, nickel and iron commercially known as aluminum-nickel magnet alloy. It has Ibeen determined that if magnets of this material are employed, and are highly magnetized, the magnets may be made much smaller .than has heretofore been the case, and may be disposed longitudinally between the usual opposed pole-pieces, thus serving as spacing members for the pole-pieces and permitting of a construction possessing great rigidity and ruggedness. Also, by disposing .the magnets in the manner described, theb magnetic losses are considerably reduced.

' Referring to Figure 1, there are provided a pair of magnets 24 and V24 of substantially rectangular form, disposed longitudinally between the opposed pole-pleces 25 and 25' (Figures 1 and 2), the magnets serving to space the pole-pieces so as to provide a suitable gap between .the adjacent portions of the respective pole-piecesfor the introduction of thefusual armature.'` The polepieces and magnets are maintained in assembled relation and are firmly secured Vto the backing plate I6 by means of bolts 26, the upper and lower surfacesof .the respective magnets being provided with grooves for the reception or the bolts, thus enhancingthe ruggedness and rigidity of the construction. During the assembly ol the magnets 'and pole-pieces, the usual coil 21 is disposedbetwee'n the pole-pieces, inwardly of the magnets as illustrated. An armature 28 is dis-- spaced centrally in the gap between the upper tips of the respective pole-pieces. At its lower end the armature 28 is secured, by screws or other suitable means, to a downwardly extending projection 30 of a bridge 3|; which is adjustably mounted upon the lower faces of the respective pole-pieces in a manner now to be described.

The bridge 3l may be formed as illustrated in Figure 3, a portion of .the material being struck downwardly to form the projection 30, leaving the bridge in -the form of a bifurcated member. The bifurcated end of the bridge is secured to the adjacent pole-piece by means of screws, one or more gaskets 32 being interposed between the bridge and the pole-piece in order to provide al fulcrum for rocking adjustment of the bridge. The opposite end of the latter is adjustably secured to the pole-piece 25' by means of screws 33 and 33' which are journalled in the bridge and threaded into the pole-piece 25'. An intermediate adjusting screw 34 is threaded in the bridge between the screws 33 and 33 and has its inner end in engagement with the adjacent face of the pole-piece 25'. The angular position of the bridge 3l, and hence the position of the armature 28, may be regulated by adjusting the screws 33 and 33 in one direction and the screw 34 in the opposite direction.

A member 35 of insulating material is secured to the upper surface of the pole-piece 25' and Aprovides a support for the terminals 36 and 31,

which may be secured thereto in any suitable fashion, it being the intention that the respective ends of the wire constituting the coil 21 shall ybe connected, as by solder, to the respective terminals 36 and .31, by means of which they are similarly connected to the respective leads of the telephone circuit (not shown).

From the foregoing description it will be apparent that the present invention provides a telephone instrument of the class described which is exceedingly compact, emcient and rugged. It will likewise be appreciated that the instrument is capable of very delica/te adjustments, which ad y j'ustments are more or less permanent, due to the fact that the armature mounting is of such a na.- ture not to be easily displaced or thrown out of adjustment. a

In practice it is preferred to make the magnets 24 and 24' of the material specified above, while the pole-pieces 25 and 25'vand armature 28 are .made of a high grade-silicon steel. The diaphragm is preferably duralumin, while the back' ing 'plate I3 and bridge 3| are preferably of brass able materials. The coil 21 may consist of about 1000 turns of from No;` 37 to No. 40 AWG copper wire. The core is preferably of Bakelite or similar material, but may be of any suitable nonconducting and non-magnetic material.

It will be readily appreciated that, because of the relative location and disposition of the magnets 2l, 24 and pole-pieces 25,` 25', the present construction lends itself admirably to a mode of assembly in which the core, pole-pieces and magnets are assembled, after which a magnetizing force is' applied, through suitable instrumentalities, to -magnetize the permanent magnets 2l and" v24'. It will be readily appreciated that ease of Likewise, the 4 assembly is thus promoted, since it is much more convenient, in assembling the elements, to with unmagnetized members.

A more important advantage of magnetization after assembly resides in elimination o'f the loss deal in magnetization incurred in breaking the magnetic circuit, which loss is unavoidable when the magnetization is carried out prior -to assembly of the device. This loss amounts to thirty per cent, more or less, of 'the total magnetic force of the magnets, and it is therefore apparent that by devising a structure in which the permanent magnets may be magnetized after-assembly, the applicants are enabled to, reduce the size of the magnets by approximately thirty per cent.`

Figures 5, 6 andl 7 -illustrate a modicationl oi? the manner previously described. The lower end of the armature is secured in an aperture 42 provided for that purpose in a bridge 42', by means of tight-fitting insulating spacers 43 and 44. The width of the aperture 42 is made to correspond with the gap between the lower tips of the respective pole-pieces, andthe spacers 4l and 44, together with the armature 40, completely fili this gap, -thus 'centering the armature permanently therein. Preferably the non-magnetic spacers 43 and 44 and the armature 40 are permanently affixed to the bridge 42' as by solder, and it`is obvious that the spacers 4 3 and 44 may, if desired, be comprised of a single strip of material folded over the end of the armature 4l before betweenv the bridge 42' and the lower surfaces;

of the respective polepieces.-

Preferably the bridge 42' is provided with up'- turned projections 45 and 46 (Figure 6) for engagement in suitable sockets provided in the lower. face of the coil core 41, facilitating assembly and enhancing the rigidity of the structure.

In the device illustrated in Figures s and 9, the magnets and 5l serve to space the polepieces 5i, 5|', 52, I2', asin the -case of the previous constructions," and the amature 53 is coupled to the diaphragm I4 in the'manner prises a pair of non-magnetic bridge members I1, l1' disposed above the lower pole tips of the respective pole-pieces arid secured to the inwardly extending horizontal projections of the respective pairs of opposed pole-pieces as by means of screws. Thus these bridge members are disposed -j i between the lower end of the coil il andthe upper edges of the respective lower pole tips. The

armature 53 is received between the adjacentv edgesoLthe bridge members 51 and 51"-respec tively, the latter being provided, for this purpose, with slots Il., 58' (Fig. 8) substantially correspondingy to the thickness of the armature. Preferably the armature issecured to the` respective bridge members by soldering.

By the described construction both ends of the Y armature are permitted to vibrate'within their respective air gaps, thus considerably increasing the sensitivity of the instrument, and giving it an improved/voice frequency response. Since the armature bridge is positioned below the coil, it

is not necessary -to increase the internal diameter ofthe coil core, or to decrease the effectiveness of the coil in-any mannen Figure 10 illustrates a modification which may be applied to any of the previously described constructions. In this case, the armature B0-may be coupled to the diaphragm in the manner previously described, and may also be secured at its lower end in any suitable manner, as for ax-- ample, in the manner illustrated infFigure 5. The usual coil, such as the coil 21 of Figure 1, or the coil Il of Figure 9, is omitted,- and the amature itself is provided with a coil 6I, having a much ,smaller number of turns than the; coils 21 and Il. For example; the coil Il may comprise approximately 100 turns of No. 38 to No. 40 AWG wire. The coil is roughly conical in shape, the greatest concentration of turns occurring nearestA the lower'end of the armature. which is rigidly secured. By lthus-expedient, the natural vibration period of the armature is not substantially affected by placing the .turns directly upon the armature, andthe sensitivity ofthe instrument is therefore not impaired. .On the other hand, `by reason of the coil 6I Vbeing wound directly,

. upon the amature 60, the efficiency of the instrument is greatly increased for reasons which will be obvious. Due to the lower numberof turn s,'the generated `voltage will be correspond. ingly low, but may be increased by the use of a step-up transformer-:62, if desired, the secondary coil of the latter being connected in the telephone circuit. l Ifdesired, thev armature 60 may be supported in a mannerdescribed in connection with Figur'esj and 9 and illustrated therein.

previously described. 'Inv the present construction it is preferable to employ' a pair of polepieces -for each magnet, 'and the polerpieces are of somewhat different-form from: those of pre--v 55 which serves as a supporting memand an inturned pole tip 56. The opposed pole- -r piece 5i is formed in a similar but opposite manvner so as to complement the pole-piece llin forming a support for the armature bridge and' an air gap for the reception of the amature 53. The pole-pieces 5I and Slf extend laterally to the center of the amature, and a s pair of pole-pieces 52 and l2' are provided'therebescribed by tle-fiespective opposed pairs oil/pole l tips, andare connected in the telephone circuit yond, for cooperation with the magnet It "i in the usual manner. The armature 1i is prcfme 11-13 illustrate a further mourned form 'ot instrument employing a single '.magnetof` increased size, two coils,` and an armature secured atboth ends and having its midpoint coupled to the diaphragm.. 'In' this construction, asy inthe. y

previous constructions, the magnet 10 serves to space the 4pole-pieces 1I and 1i',- the latter being l spaced at-their upper ends by sleeves 12. The pole-pieces 1| and 1 i are provided with inwardly projecting U-shape'd pole-tip members 13 and13' respectively, secured'thereto by welding or in any suitable fashion, there being four pole 'tips associated with each polepiece, thus constituting four air gapsinall "Coils 1`4and 1S are disposed in the 'usual ginanner within the spaces circum- In this construction the armature bridge com- I in the previously described constructions, and is coupled to the diaphragm (not shown) in the usual manner, except that in this case the armature 16 has its midpoint, rather than oneof its ends, coupled to the diaphragm. Each end of the armature 18 is adiustably mounted by means now to be described. Since the respective lends of the amature are similarly mounted, only one mounting will be described.

Referring to Figure 13, an end of the armature 16 is secured between an armature adjusting block 11 and an amature plate 18 by means of screws 19, 19', the latter being journalled in the block 11 and plate 18, and being threaded into the backingplate 80. The end of the adjusting block 11 adjacent the backing plate 80 is provided with an integral projectionF 8l for engagement v with the surface of the backing plate 80 to serve as a tulcrum. It will be apparent that the block 11 may be rocked laterally about the fulcrum 8l by loosening one of the screws 19 and 19' and tightening the other screw, the projection 8| of the block 11 being at all times maintained in engagement with the backing plate 80. It will be understood that by rocking the respective adjusting blocks 11 the armature 16 may be suitably adjusted within the several air gaps.

By the use of an unusually long and thin armature, in the construction just described, it Will be understood that the instrument is rendered considerably more sensitive, and is also more etlicient by reason of the reduction of eddy-.currentlosses in the armature and pole-pieces. Also, since the armature is mounted at both ends, the device has increased structural stability.

The modification just described lmay be-l extended to a device in which the armature may have, instead of the two arms illustrated, a greater number of arms, each vibrating within its own coil and air gaps, all of the arms of the arma- ,l ture being, of course, in the same plane, and extending radially from the point of connection between the armature and the diaphragm. 1 In such a device the outer end of each arm ofthe armature is preferably mounted adjustably in the manner described. i 1

It will be apparent to those skilled in the art that certain of the features above described are interchangeable between the various forms and modiiications embraced in the present invention.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is: v

1. In a telephone instrument, a pair of opposed pole-pieces having inwardly projecting pole-'tips deiining an air-gap between said pole-pieces,i permanent magnets disposed lengthwise between and spacing said pole-pieces and serving to fix said air-gap, connecting means .extending between said kpole pieces and engaging said magnets 4for erably longer and thinner than those employed .the space between said pole-pieces, a vibratory armature supported on said bridge and extending between said pole-tips, a diaphragm connected to said armature, .and a coilsurrounding said armature and adapted to be connected in a telephone circuit, said coil being supported on and insulated from said armature.

3. In a telephone instrument, a magnetic circuit comprising a permanent magnet and opposing pole-pieces, a vibratory armature supported between said pole-pieces, adiaphragm connected to said amature, and a coil surrounding said armature and adapted to be connected in a telephonecircuit, said coilbeing supported on and. insulated from said armature and being of decreasing radial thickness toward the point of connection of said armature to said diaphragm.

4. In a telephone instrument, a pair of opposed pole-pieces having inwardly projecting pole-tips deilning an air gap between said pole-pieces, permanent magnets disposed lengthwise between and spacing said pole-pieces and serving to x said air gap, connecting means extending between said pole pieces and engaging said magnets for maintaining the latter in place between said pole pieces, a non-magnetic bridge member spanning the space between said` pole-pieces, a vibratory armature supported on said bridge and extending between said pole-tips, a diaphragm connected to said armature, and a coil surrounding said arma. ture and adapted to be connected in a telephone circuit, said armature being` spaced between said pole-pieces by means of non-magnetic spacing members disposed between the end of said armature supported on said bridg'e and the adjacent ends of said respective pole-pieces.

5. In a telephone instrument, a pair of opposed pole-pieces having inwardly projecting pole-tips defining an air gap between said pole pieces, permanent magnets disposed lengthwise between and spacing said pole-pieces and serving to fix said air gap, connecting means extending between said pole pieces and engaging said magnets for main-v maintaining the latter in place between said pole 1 pieces, a non-magnetic bridge member spanning taining the latter in place between said pole pieces, a non-magnetic bridge member spanning the space between said pole-pieces, a vibratory armature supported on said bridge and extending between said pole-tips, a diaphragm connected to said armature, and a coil surrounding said armature and adapted to be connected in a telephone circuit, said armature being spaced between said pole-pieces by means of non-magnetic spacing members disposed and filling the space between the endof said armature supported on said bridge and the adjacent ends of said respective polepieces.

6, In a telephone instrument, a pair of opposed pole-pieces having inwardly projecting p ole-tips defining an air gap between said pole-pieces, permanent magnets disposed lengthwise between and spacing said pole-pieces and serving to iix said air gap, a non-magnetic bridge member spanning the space between said -pole-pieces, a vibratory armature supported on said bridge and extending between said pole-tips, a diaphragm connected to -said armature, and a coil surrounding said armature and adapted to be connected in a telephone circuit, said bridge member being mounted i'or rocking movementrelative to said pole-pieces.

7. Ina telephone instrument, a pairof opposed pole-pieces having. inwardly projecting pole-tips deiining an air gap between said pole-pieces, permanent magnets disposed lengthwise between and spacing-said pole-pieces and serving to fix said air gap, a non-magnetic bridge member spanning the space between said pole-pieces, a vibratory armature supported on said bridge and extending between said pole-tips. a diaphragm connected to said armature, and a coil surrounding'said armature and adapted to be connected in a telephone circuit, said bridge member being disposed adjacent one end of said coil and inwardly the ad- Jan Dole-tins, and providing a mvo support for said amature. if

8. In a telephone instrument, a telephone motor including spaced pole-pieces having inwardly projecting pole-tips, a coil, andan amature exs pole-tips and said coli extending into relatively close relation to said bridge member. v

9. In a telephone instrument, -a telephone motor including a pair o! opposed pole-pieces having r inwardly projecting pole-tips defining an air gap between said pole-pieces. permanent magnets disposed lengthwise between and spacing the respective pole-pieces of said pair and serving to nx said air gap, connecting means extending between said pole-pieces for maintaining said magnets in place between said pole-pieces, an armavtime extending between said pole-tips, means supporting said armature for vibrator! movement. a diaphragm,- and means connecting said diayis phragm and said amature.

ARTHUR 'rURNBULn Jn.: l

' HERBERT R. WARNKE. 

